(4ei) Novel Design of Gene/Drug Delivery Systems by Virus-Polymer Hybrid

My research focus has been the design and characterization of novel and efficient gene delivery systems by engineering viral vectors to target specific cell types. Currently, I am working on a rational design of virus-polymer hybrid to achieve more stable and enhanced gene/drug delivery system in vitro and in vivo.

(1) Targeted Gene Delivery with Viral Vectors

One of the most challenging problems in virus-mediated gene therapy is how the gene can be specifically delivered into the target tissues or cells. Our lab has developed a novel and efficient strategy that allows the retro/lentiviral vectors to enter specifically into the target cell. This innovative design is based on engineering retro/lentiviral vectors by altering the viral envelope glycoprotein (Env), the protein that is responsible for binding the virus to cell surface receptors and for mediating entry. Compared with conventional methods that manipulate the delicate coupling interactions of the binding and fusion domains of Env glycoprotein, which usually causes decreased viral infectivity, our engineering approach involved the incorporation of a targeting antibody and pH-dependent fusogenic protein as two distinct molecules on the viral surface. A major advantage of this scheme over others where the viral protein is engineered with a foreign binding component is that the fusion protein maintains its full biological activity so that viral titer is not killed for increased specificity. This targeting methodology is flexible and can be extended to other forms of cell type-specific recognition with the different targeting antibody (or other cell-binding protein) to mediate targeting. The flexibility and broadness of this method will facilitate the application of targeted gene delivery for therapy and research.

(2) Development of Quantum dot labeling of gene delivery vectors for visualization of viral transduction pathways

During viral entry, the virus interacts with various cellular structures and takes advantage of their environments to optimize the delivery of the viral genome to the nucleus and promote efficient viral replication. Improved understanding of their interactions can provide crucial insights for preventing virus-triggered diseases, as well as enhancing the efficacy of virus-mediated gene delivery. The ability to track individual viruses is a powerful tool for investigating viral infection routes and characterizing the dynamic interactions between viruses and target cells. As quantum dots have several advantages of remarkable photostability and brightness over conventional organic dyes, they are emerging as a fluorescent probe for biological imaging and medical diagnostics. We have established a general method of labeling enveloped viruses with semiconductor quantum dots (QDs) for use in single virus trafficking studies. Retroviruses, including human immunodeficiency virus (HIV), could be successfully tagged with QDs through the membrane incorporation of a short acceptor peptide (AP) that is susceptible to site-specific biotinylation and attachment of streptavidin-conjugated QDs. We have also demonstrated a strategy for linking adeno-associated virus (AAV) with quantum dots through a coupling reaction. These labeling methods can provide an attractive tool for elucidating intracellular processes of many kinds of viral and non-viral vectors in a detailed manner.

(3) Sustained and Enhanced gene/drug delivery systems by virus-polymer hybrid

Currently, in my postdoctoral research, I am exploring a novel design of virus-polymer hybrid system for enhanced stability and gene transduction efficiency in vivo. The design and evaluation of gene/drug delivery systems for sustained and localized release profiles to target sites of interest is desirable for the prolonged treatment and the precise introduction of therapeutic products, alleviating the concern of an off-targeting effect. Biomaterial scaffolds can provide an environment that facilitate tissue/cell adhesion (mechanical support) and allows drug/gene delivery vectors to be employed for the sustained release in a spatially controlled manner. In this study, we have investigated a strategy based on a porous scaffold of PLGA polymer associated with other immunostimulatory molecules (i.e. cytokines) and foreign substances (antigen) or viral vectors such as adenovirus and lentivirus to recruit host dendritic cells and further educate them in situ for developing immune defenses. In two weeks after implantation, the recruitment of dendritic cells (CD11c+) was observed in the implant. Antigen-specific immune responses with different combination of cytokines and antigens or viral vectors will be addressed in more detail.

References

Kye-Il Joo and Pin Wang. Visualization of targeted transduction by engineered lentiviral vector. Gene Ther. 2008, 15: 1384-96

Kye-Il Joo, Yuning Lei, Chi-Lin Lee, Jonathon Lo, Jiansong Xie, Sarah F. Hamm-Alvarez, and Pin Wang. Site-specific labeling of enveloped viruses with quantum dots for single virus tracking. ACS Nano, 2008, 2: 1553-1562

Kye-Il Joo, April Tai, Chi-Lin Lee, Clement Wong, and Pin Wang. Imaging multiple intermediates of single-virus membrane fusion mediated by distinct fusion proteins. Microsc. Res. Tech. 2010, Accepted.